U.S. patent application number 10/613081 was filed with the patent office on 2004-07-29 for composition, organic conductive layer including composition, method for manufacturing organic conductive layers, organic el element including organic conductive layer, method for manufacturing organic el elements, semiconductor element including organic conductive layer, method for manufacturing sem.
This patent application is currently assigned to SEIKO EPSON CORPORATION.. Invention is credited to Kimura, Hideyuki, Kuwashiro, Shingo, Seki, Shunichi, Tanabe, Seiichi.
Application Number | 20040144975 10/613081 |
Document ID | / |
Family ID | 32032831 |
Filed Date | 2004-07-29 |
United States Patent
Application |
20040144975 |
Kind Code |
A1 |
Seki, Shunichi ; et
al. |
July 29, 2004 |
Composition, organic conductive layer including composition, method
for manufacturing organic conductive layers, organic El element
including organic conductive layer, method for manufacturing
organic El elements, semiconductor element including organic
conductive layer, method for manufacturing semiconductor elements,
electronic device, and electronic apparatus
Abstract
To provide a composition in which the viscosity is hardly
changed with the passage of time and an organic conductive layer
including the composition in order to planarize the surface of a
layer formed by an inkjet process and in order to stabilize the
properties. A composition according to the present invention
contains an organic conductive material and at least one species of
solvent, wherein the changing rate of the viscosity thereof is
within a range of .+-.5% when 30 days have passed after the
preparation. The solvent preferably contains a glycol medium. An
organic conductive layer according to the present invention
includes the composition having the above configuration.
Inventors: |
Seki, Shunichi; (Suwa-shi,
JP) ; Tanabe, Seiichi; (Shiojiri-shi, JP) ;
Kuwashiro, Shingo; (Chino-shi, JP) ; Kimura,
Hideyuki; (Suwa-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
SEIKO EPSON CORPORATION.
Tokyo
JP
|
Family ID: |
32032831 |
Appl. No.: |
10/613081 |
Filed: |
July 7, 2003 |
Current U.S.
Class: |
257/40 |
Current CPC
Class: |
H01L 51/0034 20130101;
H01L 51/0007 20130101; H01L 51/0081 20130101; H01L 51/5048
20130101; H01L 51/0035 20130101; H01L 51/0022 20130101; H01L
51/0037 20130101; H01L 51/0038 20130101; H01L 51/0005 20130101;
H01L 51/5088 20130101; H01L 51/0078 20130101 |
Class at
Publication: |
257/040 |
International
Class: |
H01L 035/24 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2002 |
JP |
2002-329348 |
Aug 2, 2002 |
JP |
2002-226563 |
Claims
1. (Currently Amended) A composition, comprising: an organic
conductive material and at least one species of solvent, wherein
the changing rate of the viscosity is within a range of .+-.5% when
30 days have passed after the preparation.
2. (Currently Amended) The composition according to claim 1, the
solvent containing a glycol medium.
3. (Currently Amended) The composition according to claim 2, the
content of the glycol medium in the solvent ranging from 40 to 55
percent by weight.
4. (Currently Amended) The composition according to claim 2, the
glycol medium including diethylene glycol and a mixture containing
the same.
5. (Currently Amended) The composition according to claim 2, the
glycol medium including monoethylene glycol and a mixture
containing the same.
6. (Currently Amended) The composition according to claim 2, the
glycol medium including triethylene glycol and a mixture containing
the same.
7. (Currently Amended) The composition according to claim 1, the
organic conductive material including polythiophene
derivatives.
8. (Currently Amended) The composition according to claim 1, the
organic conductive material including a mixture of
polydioxythiophene and polystyrene sulfonic acid.
9. (Currently Amended) The composition according to claim 1, the
organic conductive material including a mixture of polyaniline and
polystyrene sulfonic acid.
10. (Currently Amended) The composition according to claim 2, the
solvent containing an acetylenic alcohol surfactant.
11. (Currently Amended) The composition according to claim 10, the
content of the acetylenic alcohol surfactant in the solvent ranging
from 0.01 to 0.1 percent by weight.
12. (Currently Amended) The composition according to claim 10, the
acetylenic alcohol surfactant having a boiling point that is less
than or equal to that of the medium as well as the surfactant
contained in the solvent.
13. (Currently Amended) The composition according to claim 10, the
acetylenic alcohol surfactant includes
3,5-dimethyl-1-octyne-3-ol.
14. (Currently Amended) The composition according to claim 1, the
composition being subjected to degassing treatment.
15. (Currently Amended) The composition according to claim 14, the
degassing treatment being performed at a vacuum pressure that is
less than or equal to the saturation vapor pressure of water.
16. (Currently Amended) The composition according to claim 14,
before the degassing treatment, the composition contain containing
an amount of the medium vaporized in the degassing treatment in
advance.
17. (Currently Amended) An organic semiconductive layer,
comprising: a composition according to claim 1.
18. (Currently Amended) A method for to manufacture organic
conductive layers, comprising: applying a composition to different
portions by an inkjet process, the composition being set forth in
claim 1.
19. (Currently Amended) The organic conductive layer-manufacturing
method according to claim 18, further comprising: removing a
solvent after the application step.
20. (Currently Amended) The organic conductive layer-manufacturing
method according to claim 19, the removing being performed in a
vacuum atmosphere.
21. (Currently Amended) The organic conductive layer-manufacturing
method according to claim 20, the removing being performed at a
pressure of 1.333.times.10.sup.-3 Pa or less and a temperature
substantially equal to room temperature.
22. (Currently Amended) The organic conductive layer-manufacturing
method according to claim 19, further comprising: performing
thermal treatment at 100.degree. C. or more after the removing.
23. (Currently Amended) The organic conductive layer-manufacturing
method according to claim 22, a heat source used in the thermal
treatment including infrared rays.
24. (Currently Amended) An organic EL element, comprising: a hole
injection/transport layer including the organic conductive layer
according to claim 17.
25. (Currently Amended) A method for to manufacture organic EL
elements, comprising: forming hole injection/transport layers each
including the organic conductive layer according to claim 17 by an
inkjet process.
26. (Currently Amended) An electronic device, comprising: at least
the organic EL element according to claim 24 and a circuit to drive
the organic EL element.
27. (Currently Amended) An electronic apparatus, comprising: the
electronic device according to claim 26.
28. (Currently Amended) An organic semiconductor element,
comprising: a source, a drain, a gate or wiring lines, which are
conductive portions included in an integrated circuit, each
including the organic conductive layer according to claim 17.
29. (Currently Amended) A method for manufacturing organic
semiconductor elements, comprising: forming a drain, a gate or
wiring lines, which are conductive portions included in an
integrated circuit, by an inkjet process using the organic
conductive layer according to claim 17.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a composition to form
conductive layers included in electronic devices, an organic
conductive layer including such a composition, a method to
manufacture organic conductive layers, an organic EL element
including the organic conductive layer, a method to manufacture
organic EL elements, a semiconductor element including the organic
conductive layer, a method to manufacture semiconductor elements,
an electronic device, and an electronic apparatus. In particular,
the above conductive layer is used as a conductive portion to form
electrodes and wiring lines included in electronic circuits or
integrated circuits. The composition according to the present
invention can be used for raw materials for various coating
processes. An inkjet process is preferably used when organic
conductive layers are formed using the composition.
[0003] 2. Description of Related Art
[0004] In the related art, a photolithographic process has been
used for forming wiring lines included in electronic circuits or
integrated circuits. In such a photolithographic process, a
photosensitive material called a resist material is provided above
a substrate covered with a conductive layer. A circuit pattern is
irradiated and then developed. The conductive layer is then etched
along the resist pattern, thereby forming wiring lines. In the
photolithographic process, there is a problem in that a complicated
process and a large system, such as a vacuum unit, must be used.
The manufacturing cost is high because the utilization efficiency
of raw materials is several percent and therefore most of the raw
materials are wasted. The energy efficiency of the manufacturing
process is low.
[0005] A conductive layer pattern used for the above integrated
circuit or thin-film transistors contains metal, such as copper or
aluminum, or indium tin oxide (ITO) and a semiconductor layer
pattern used therefor contains silicon in many cases. In the
related art, such patterns have been formed according to the
following procedure in general. A conductive or semiconductor layer
is formed over a substrate by a thermal, plasma, or optical CVD
process or the like and unnecessary portions of the layer are then
removed by a photolithographic process.
[0006] However, in a method for forming a thin-film pattern by a
combination of the CVD process and the photolithographic process,
there are the technical problems below from a process
viewpoint.
[0007] (1) When a substrate on which a thin-film is formed has, for
example, an irregular surface, a thin-film having a uniform
thickness and uniform properties is hardly formed on the substrate
because gaseous raw materials are used.
[0008] (2) The productivity is low because the rate of forming a
thin-film is low.
[0009] (3) When the plasma CVD process is used, the costs of
purchasing and maintaining a manufacturing apparatus are high
because a complicated, expensive high frequency wave-generating and
a vacuum unit are necessary.
[0010] (4) The manufacturing cost is high because the
photolithographic process is complicated and the utilization
efficiency of raw materials is low, and the cost of treating waste
is also high because a large amount of resist materials and etching
solutions are discarded.
[0011] Furthermore, in a method for forming a silicon thin-film
pattern, there are the technical problems below from a material
viewpoint.
[0012] (5) Raw materials are hard to handle because the raw
materials contain gaseous silicon hydride having high toxicity and
reactivity.
[0013] (6) In addition, a sealed vacuum unit and piping system must
be used because the gaseous raw materials are used. In general, a
manufacturing apparatus including such a vacuum unit and piping
system is massive and such an apparatus is operated in a clean
room. Hence, the maintenance cost is high.
[0014] (7) The production cost is high because the above vacuum
unit and piping system are expensive and a large amount of energy
is consumed in order to form a desired thin-film in such a manner
that the vacuum environment and plasma environment are
maintained.
[0015] In contrast, the following method has been proposed. Liquid
(hereinafter referred to as a composition) containing conductive
fine particles dispersed therein is applied onto a substrate by an
inkjet process so as to form a pattern directly and the applied
liquid is then transformed into a conductive layer pattern by
thermal treatment or the application of a laser beam (see, for
example, U.S. Pat. No. 5,132,248). Furthermore, the following
method has been proposed. Bus and address electrodes for plasma
displays are formed by an inkjet process using ink containing
silver nanoparticles dispersed therein (see, for example, Tech.
Digest of SID '02, pp. 753 (2002). According to these methods, the
above photolithographic process is not necessary, a process for
forming conductive layers can be greatly simplified, and the
consumption of raw materials can be reduced. Thus, the methods are
fit for manufacturing the above-mentioned electronic circuits and
integrated circuits and it is expected that the methods contribute
to the reduction of manufacturing cost.
[0016] However, in order to form wiring lines, the conductive fine
particles must be stacked to a certain degree so as to form a thick
layer. That is, if the conductive fine particles are not
accumulated, portions in which the conductive fine particles are
not in contact with each other cause breaks in wiring lines. If the
layer thickness is insufficient, the electric resistance is high,
that is, obtained wiring lines are inferior in conductivity.
[0017] In the method for directly applying the liquid containing
the conductive fine particles dispersed therein onto a substrate by
an inkjet process so as to form a pattern directly, the amount of
the conductive fine particles provided by discharging the liquid at
a constant rate is limited due to the viscosity of the discharged
liquid because the liquid contains the conductive fine particles
dispersed therein. When a large amount of the liquid is ejected in
one shot, it is difficult to adjust positions for forming wiring
lines and such wiring lines have a large width, which is not
suitable for the integration of electronic circuits or the
like.
[0018] The relationship between the above-mentioned inkjet process
and the composition used in the process has been examined for the
following technical subjects in a wide range.
[0019] (1) A method for manufacturing organic EL elements each
including corresponding hole injection/transport layers formed by
an inkjet process using a composition containing a polar solvent
and a hole injection/transport material (see, for example, Japanese
Patent Application No. 10-248816)
[0020] (2) A method in which a composition can be constantly
discharged by an inkjet process and satisfactory patterning and
layer-forming properties can be obtained when the composition
contains an aprotic cyclic solvent, such as DMI or NMP (see, for
example, Japanese Patent Application No. 11-134320)
[0021] (3) A method in which PEDOT/PSS is used as a hole
injection/transport material (see, for example, Japanese Unexamined
Patent Application Publication No. 2000-91081)
[0022] (4) A method in which plugging can be prevented by the use
of a composition containing a glycol solvent having a high boiling
temperature (see, for example, Japanese Unexamined Patent
Application Publication No. 2001-167878)
[0023] (5) A method in which plugging can be prevented, the
flatness of layers formed using this composition is satisfactory,
and an interface can be prevented from being formed by the use of a
composition containing a solvent having a predetermined volatility
(vapor pressure) (see, for example, Japanese Unexamined Patent
Application Publication No. 2001-52861)
[0024] In contrast, a method in which a conductive coating is
formed by a screen printing process using paste has been proposed
(see, for example, PCT Japanese Translation Patent Publication No.
2002-500408). Since paste has high viscosity in general, paste is
not fit for an inkjet process.
[0025] On the other hand, Kawase et al. disclosed the following
technique in Science: the above material PEDOT/PSS is used for
forming source and drain electrodes when organic TFTs are prepared
by an inkjet process (see, for example, Science, 15 December 2000,
Vol. 290, pp. 2123-2126).
SUMMARY OF THE INVENTION
[0026] Related art liquid containing a semiconductive material or a
conductive material, such as the above-mentioned conductive fine
particles or a conductive polymer, that is, a related art
composition has a certain viscosity at the instant that it is
prepared. However, there is a problem in that the viscosity of the
composition is gradually changed with the passage of time and
therefore the viscosity at the instant that the composition is
prepared is greatly different from the viscosity at the instant
that the composition is discharged.
[0027] The significant change in viscosity due to the passage of
time causes the following problems. It is difficult to control the
amount of ejected droplets and the flatness of layers each disposed
between banks is deteriorated. Furthermore, the fact that the
composition changes with the passage of time means that there is a
problem in that changes in the properties of obtained conductive or
semiconductive layers are caused.
[0028] Once such layers having an irregular surface have been
formed, the surface flatness cannot be improved by drying or
heating treatment. For example, when a conductive layer having such
an irregular surface is used for forming wiring lines, the
following problems are caused. The presence of irregular portions
disturbs the flow of electrons or holes passing through the
conductive layer, stable conduction cannot be obtained, and the
long-term reliability is deteriorated.
[0029] Furthermore, when some layer is placed on the conductive
layer having the irregular surface, the placed layer is rendered
irregular due to the shape of the conductive layer. Electronic
circuits and integrated circuits including the above conductive
layer and the layer placed thereon are inferior in stability during
operation and long-term reliability.
[0030] Thus, there are problems in the formation of a layer pattern
by an inkjet process and the properties of an element obtained
thereby because the viscosity of the related art composition cannot
be maintained constant.
[0031] The present invention has been made to address the above
fact. In order to obtain a layer, formed by an inkjet process,
having a flat surface and in order to enhance the properties of
functional layers formed by the above process and the reliability
of elements, an aspect of the present invention provides a
composition in which the viscosity hardly changes with the passage
of time, an organic conductive layer including such a composition,
a method to manufacture organic conductive layers, an organic EL
element including the organic conductive layer, a method to
manufacture organic EL elements, a semiconductor element including
the organic conductive layer, a method to manufacture semiconductor
elements, an electronic device, and an electronic apparatus.
[0032] In order to address the above problems, an aspect of the
present invention provides a composition containing an organic
conductive material and at least one species of solvent, wherein
the changing rate of the viscosity is within a range of .+-.5% when
30 days have passed after the preparation.
[0033] In the composition containing the above components, the
viscosity can be maintained constant for an extremely long time as
compared with the related art. Therefore, the thickness of a
coating including the composition can be securely reduced or
prevented from changing with the passage of time, thereby obtaining
a conductive layer, semiconductive layer, and semiconductor element
having high reliability.
[0034] The composition containing the above components is
satisfactory in long-term storage property because the changing
rate of the viscosity is small. Furthermore, the composition can be
marketed alone and used in various industrial applications because
the composition can be manufactured at low cost by a mass
production process.
[0035] The solvent, which is a component of the composition
according to an aspect of the present invention, preferably
contains a glycol medium. Thereby, the changing rate of the
viscosity of the composition can be greatly decreased. In this
case, when the content of the glycol medium in the solvent ranges
from 40 to 55 percent by weight, plugging can be reduced or
prevented while the composition is discharged from nozzle holes by
an inkjet process. Furthermore, the discharged composition can be
reduced or prevented from flying in an arc, that is, the discharged
composition can fly in a straight line so that layers are formed,
thereby enhancing the flatness and the surface profile of the
obtained layers. Thus, in an organic EL element including a hole
injection/transport layer formed using each layer described above,
the pixel flatness is greatly enhanced.
[0036] The above glycol medium includes diethylene glycol and a
mixture containing the same, monoethylene glycol and a mixture
containing the same, and triethylene glycol and a mixture
containing the same.
[0037] The organic conductive material contained in the composition
according to an aspect of the present invention includes
polythiophene derivatives, a mixture of polydioxythiophene and
polystyrene sulfonic acid, and a mixture of polyaniline and
polystyrene sulfonic acid.
[0038] The solvent contained in the composition according to an
aspect of the present invention contains an acetylenic alcohol
surfactant, whereby the dispersibility of the above material can be
enhanced.
[0039] Furthermore, the surface tension of the composition can be
reduced, whereby the wettability to a substrate can be enhanced.
Since the above surfactant is characterized in that bubbles are
hardly formed, bubbles can be reduced or prevented from remaining
in the composition, thereby obtaining uniform, dense layers having
no defect. In particular, when the composition according to an
aspect of the present invention contains 0.01 to 0.1 percent by
weight of the acetylenic alcohol surfactant, layers including the
composition are satisfactory in flatness.
[0040] When the acetylenic alcohol surfactant has a boiling point
that is less than or equal to that of the medium as well as the
surfactant contained in the solvent, the drying time of layers
prepared by discharging the composition can be adjusted to that of
the solvent, thereby reducing or preventing the surfactant from
remaining after the removal of the solvent. Therefore, the layers
including the composition containing the above components are
usually satisfactory in flatness and uniformity. When a
hard-to-remove surfactant, for example, a surfactant having a high
boiling point, is used, the properties of conductive layers and
semiconductive layers are deteriorated due to the remaining
surfactant in some cases. In particular, the acetylenic alcohol
surfactant is preferably 3,5-dimethyl-1-octyne-3-ol.
[0041] When the composition according to an aspect of the present
invention is subjected to degassing treatment, the discharging
stability of the composition discharged form nozzle holes by an
inkjet process is enhanced, thereby enhancing the flatness and
surface profile of obtained layers. Thus, for example, organic EL
elements, each including corresponding hole injection/transport
layers including the above layers are securely enhanced in pixel
flatness.
[0042] The degassing treatment includes vacuum treatment,
ultrasonic treatment, membrane separation, heating treatment, and
gas replacement. The vacuum treatment is preferably used because
gas can be continuously removed without depending on the viscosity.
When the membrane separation is employed, a membrane (gas-liquid
separating membrane) having high solvent resistance must be
used.
[0043] In the degassing treatment, the component ratio of the
composition is apt to change due to the vaporization of volatile
components. In particular, in the vacuum treatment, the degree of
vacuum must be increased in order to remove remaining gas more
sufficiently, whereby the component ratio of the composition is apt
to change due to the vaporization of volatile components. This
tendency is particularly strong when the composition contains a
high vapor-pressure medium, such as water. The change in component
ratio causes the deterioration of layer-forming property (flatness)
in addition to the change in characteristic and the deterioration
of discharging stability. Therefore, before the degassing
treatment, the composition preferably contains an amount of the
medium vaporized in the degassing treatment in advance. Thereby,
the component ratio of the composition can be reduced or prevented
from deviating from the optimum ratio in the degassing
treatment.
[0044] An organic conductive layer according to an aspect of the
present invention contains the above-mentioned composition.
[0045] As described above, the composition of an aspect of the
present invention has such long-term stability that the changing
rate of the viscosity is within a range of .+-.5% when 30 days have
passed after the preparation. Therefore, when such an organic
conductive layer is formed using the composition as a raw material,
the following problem can be reduced or prevented if the layer
flatness is achieved in an initial stage of the layer formation:
the flatness is deteriorated with the passage of time. Thus, the
organic conductive layer containing the above composition is fit
for mass production. Furthermore, since it is not necessary to
perform the planarizing treatment of the layer, the manufacturing
cost can be saved. When another layer is provided on the organic
conductive layer, the obtained layer can be readily planarized
without depending on the properties of the obtained layer because
the organic conductive layer is satisfactory in flatness. Thus, the
organic conductive layer is fit for electronic device applications
in which a multilayer structure is used. An organic semiconductor
element and electronic device obtained according to the above
procedure, have high reliability.
[0046] A method to manufacture organic conductive layers according
to an aspect of the present invention includes an application step
of applying the above-mentioned composition to different portions
by an inkjet process.
[0047] As described above, the composition of an aspect of the
present invention is characterized in that the changing rate of the
viscosity is small. Therefore, when the composition is discharged
from minute nozzle holes by an inkjet process, the nozzle holes
being plugged due to the change in viscosity can be reduced or
prevented. Thus, the composition can be constantly discharged from
the nozzle holes and a desired discharging rate can be constantly
achieved without depending on the period of the discharging
operation. In particular, in an organic conductive
layer-manufacturing method including an application step of
intermittently applying the composition to different portions to
form layers, the use of the composition enables the discharging
rate thereof to be precisely controlled, thereby rendering the
layer thickness uniform.
[0048] Furthermore, in the organic conductive layer-manufacturing
method including an applying step of applying the composition to
different portions by an inkjet process, layers having different
characteristics can be formed by feeding the composition, in which
the chemical makeup is gradually varied, to the nozzle holes or by
using inkjet heads each discharging corresponding compositions
different from each other. Thus, according to this manufacturing
method having the above configuration, for example, regions having
different conductive characteristics can be readily formed at
desired locations on a substrate.
[0049] The above-mentioned organic conductive layer-manufacturing
method includes a drying step of removing a solvent after the
application step.
[0050] Since the drying step of removing the solvent is provided,
the solvent is removed from the organic conductive layer formed in
the application step, thereby obtaining layers having a flat, dense
structure with high reproducibility.
[0051] In particular, when the drying step is performed in a vacuum
atmosphere, the efficiency of removing the solvent from the layers
is enhanced while the layers are maintained flat. Furthermore, when
the drying step is performed at a pressure of 1.333.times.10.sup.-3
Pa (10.sup.-5 Torr) or less and a temperature substantially equal
to room temperature, the flat organic conductive layers can be
efficiently formed in a short time. The term room temperature
herein refers to a temperature of, for example, 15 to 27.degree.
C.
[0052] The organic conductive layer-manufacturing method according
to an aspect of the present invention includes a heating step of
performing thermal treatment at 100.degree. C. or more after the
drying step.
[0053] When the organic conductive layers, from which the solvent
has been removed in the drying step, are subjected to the heating
step of performing thermal treatment at a temperature of
100.degree. C. or more, the organic conductive layers can be
rendered dense, thereby enhancing the adhesion of each organic
conductive layer to a substrate (base layer) or another layer
disposed on the organic conductive layer. The heating step is
advantageous in that the solvent, contained in the composition, for
dispersion can be sufficiently removed from the organic conductive
layers.
[0054] When an infrared ray unit is used for a heat source of the
heating step, the organic conductive layers can be efficiently
heat-treated without causing the organic conductive layer to be in
contact with the heat source, which is preferable.
[0055] An organic EL element according to an aspect of the present
invention includes each organic conductive layer functioning as a
hole injection/transport layer.
[0056] Since the organic conductive layer having the above
advantages, that is, the organic conductive layer that is
advantageous in that the flatness and uniformity are satisfactory
and the solvent can be sufficiently removed, is used as a hole
injection/transport layer, the organic EL element has invariable
element efficiency and long element life. The term element
efficiency herein refers to a luminance per unit current, and the
term element life refers to the time that elapses until the
luminance of a light-emitting element to which a current has not
applied yet decreases by half when a constant current is
continuously applied to the element.
[0057] A method to manufacture organic EL elements according to an
aspect of the present invention includes a step of forming hole.
injection/transport layers each including the organic conductive
layer by an inkjet process.
[0058] According to the organic EL element-manufacturing method
having the above configuration, the hole injection/transport layers
can be each readily formed in corresponding recessed, flat regions
having an extremely small area by an inkjet process, wherein the
hole injection/transport layers each include the organic conductive
layer from which the solvent has been sufficiently removed, the
organic conductive layer being satisfactory in flatness.
[0059] That is, in the organic EL element-manufacturing method, the
hole injection/transport layers that affect the element efficiency
and element life of the organic EL elements can be each readily
formed in corresponding desired regions by an inkjet process using
different materials. Therefore, the manufacturing cost of the
elements can be greatly reduced as compared with related art
methods using a vacuum unit. Thus, the organic EL
element-manufacturing method according to an aspect of the present
invention provides the organic EL elements having invariable
element properties at low cost.
[0060] An electronic device (referred to as an organic EL device)
according to an aspect of the present invention includes at least
each organic EL element described above and a circuit for driving
the organic EL element.
[0061] Since the electronic device having the above configuration
includes the above organic EL element having invariable element
properties, the use of the circuit to drive the element enhance the
long-term reliability.
[0062] An electronic apparatus according to an aspect of the
present invention includes the electronic device.
[0063] Since the electronic apparatus having the above
configuration includes the electronic device having high long-term
reliability, the life of the electronic apparatus can be
enhanced.
[0064] An organic semiconductor element according to an aspect of
the present invention includes a source, a drain, a gate and/or
wiring lines, which are conductive portions included in an
integrated circuit, each including the organic conductive
layer.
[0065] In the organic semiconductor element having the above
configuration, since the source, the drain, the gate and/or the
wiring lines, which are conductive portions included in an
integrated circuit, each include the organic conductive layer which
is superior in stability, hillocks (protrusions formed on a wiring
layer with the passage of time during the heat treatment or the
operation in the manufacturing steps) functioning as obstacles are
hardly formed. Thus, the passage of current can be constantly
maintained for a long time. Thereby, the organic semiconductor
element having high long-term reliability can be provided.
[0066] A method for manufacturing organic semiconductor elements
according to an aspect of the present invention includes a step of
forming a source, a drain, a gate or wiring lines, which are
conductive portions included in an integrated circuit, by an inkjet
process using the above-mentioned organic conductive layer.
[0067] According to the organic semiconductor element-manufacturing
method having the above configuration, the organic semiconductor
elements having high long-term reliability can be formed by an
inkjet process, which is a process that layers are precisely formed
(patterned) in a simple manner. Therefore, the manufacturing cost
of the organic semiconductor elements can be greatly saved as
compared with related art methods using a vacuum unit. Thus, the
organic semiconductor element-manufacturing method according to an
aspect of the present invention contributes to the production of
the inexpensive organic semiconductor elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] FIG. 1 is a schematic sectional view showing an organic
conductive layer including composition A according to an exemplary
embodiment of the present invention;
[0069] FIG. 2 is a schematic sectional view showing an organic
conductive layer including composition B according to an exemplary
embodiment of the present invention;
[0070] FIG. 3 is a sectional view showing a principal portion of an
exemplary electronic device including organic EL elements according
to an exemplary embodiment of the present invention;
[0071] FIG. 4 is a schematic sectional view showing a configuration
of a substrate included in an organic EL element according to an
exemplary embodiment of the present invention;
[0072] FIG. 5 is a schematic sectional view showing a step of
manufacturing an organic EL device according to an exemplary
embodiment of the present invention;
[0073] FIG. 6 is a schematic sectional view showing another step of
manufacturing the organic EL device according to an exemplary
embodiment of the present invention;
[0074] FIG. 7 is a schematic sectional view showing another step of
manufacturing the organic EL device according to an exemplary
embodiment of the present invention;
[0075] FIG. 8 is a schematic sectional view showing another step of
manufacturing the organic EL device according to an exemplary
embodiment of the present invention;
[0076] FIG. 9 is a side sectional view showing a schematic
configuration of an exemplary organic semiconductor element
according to an exemplary embodiment of the present invention;
[0077] FIG. 10 is a perspective view showing an exemplary
electronic apparatus including an electronic device of this
exemplary embodiment;
[0078] FIG. 11 is a perspective view showing another exemplary
electronic apparatus including the electronic device of an
exemplary embodiment; and
[0079] FIG. 12 is a perspective view showing another exemplary
electronic apparatus including the electronic device of an
exemplary embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0080] A composition according to an aspect of the present
invention will now be described in detail.
[0081] The composition of an aspect of the present invention
contains an organic conductive material and at least one species of
solvent, wherein the changing rate of the viscosity is within a
range of 35 5% when 30 days have passed after the preparation.
[0082] A combination of the organic conductive material and the
solvent contained in the composition does not depend on the
molecular weight of the organic conductive material, and any
combination may be used as long as an obtained composition has
conductivity.
[0083] The above organic conductive or semiconductive material
includes a high-molecular weight material, such as a mixture of
polydioxythiophene and polystyrene sulfonic acid, a mixture of
polyaniline and polysulfonic acid, a precursor of polyparaphenylene
vinylene, polypyrrole, or a derivative of these materials.
Furthermore, the organic conductive or semiconductive material
includes a low-molecular weight material, such as copper
phthalocyanine (CuPc), 1,1-bis(4-N,N-dinitrylaminophenyl)cyclohexa-
ne, or tris(8-hydroxyquinolinol)aluminum.
[0084] The solvent forms the composition, which is liquid, by
mixing with the organic conductive or semiconductive material. In
order to disperse the organic conductive or semiconductive material
uniformly, the solvent contains various media depending on the
material.
[0085] In particular, a polar solvent is preferably employed when a
mixture of polydioxythiophene and polystyrene sulfonic acid or a
mixture of polyaniline and polysulfonic acid, is used, wherein
these polymer materials have high conductivity. Such a polar
solvent includes, for example, water; isopropyl alcohol; normal
butanol; .gamma.-butyrolactone; N-methylpyrrolidone;
1,3-dimethyl-2-imidazolidinone and derivatives of thereof; glycols
such as diethylene glycol, monoethylene glycol, and triethylene
glycol; and glycol ethers of these glycols
[0086] The inventors have examined the above combinations for the
storage stability of the composition. As a result, the inventors
found that a decrease in changing rate of viscosity, which is one
of various characteristics of the composition, is effective in
enhancing the storage stability when the composition is prepared by
mixing an organic conductive material with at least one species of
solvent. In particular, it is known that the storage stability of
the prepared composition has a great effect on the properties and
shape of obtained layers and the properties of elements including
these layers because the composition containing the above
components is used as a raw material to prepare the layers.
[0087] However, a close examination has not been made for an
influence exerted on the properties of the layers by the changing
rate of the viscosity of the composition having the above
combination. Therefore, the inventors prepared two types of
compositions A and B shown in Table 1 and examined the changing
rate of the viscosity thereof.
1 TABLE 1 Components of Solvent Amount Composition A PEDOT-PSS
dispersion 28 g Water 22 g Diethylene glycol 50 g
3,5-dimethyl-1-octyne-3-ol 100 mg Composition B PEDOT-PSS
dispersion 28 g N-methylpyrrolidone 22 g
1,3-dimethyl-2-imidazolidinone 50 g
[0088] The term PEDOT-PSS Dispersion means
3,4-polyethylenedioxythiophene/- polystyrene sulfonic acid
(BAYTRON.sup.(P)P, manufactured by Bayer AG). Special-grade
diethylene glycol (DEG for short) manufactured by Kanto Kagaku was
used and 3,5-dimethyl-1-octyne-3-ol marketed under the trade name
of SF 61 by Air Products and Chemicals Inc. was used.
[0089] Special-grade N-methylpyrrolidone (NMP for short)
manufactured by Kanto Kagaku was used and special-grade
1,3-dimethyl-2-imidazolidinone (DMI for short) manufactured by
Aldrich Chemical Company was used.
[0090] The component ratio of the compositions shown in Table 1 was
obtained after degassing treatment. The degassing treatment was
performed by placing each composition in a chamber having a
pressure of about 160 Pa or less. In this degassing treatment, it
is known that about 4% of the solvent is vaporized. That is, media
having a relatively high vapor pressure (for example, water and so
on) are vaporized but media having a relatively low vapor pressure
(for example, DEG, NMP, DMI, and so on) are not vaporized.
Therefore, before the degassing treatment, the composition was
arranged to contain a medium (herein water) by about 4 percent by
weight higher than the optimum amount. For example, composition A
contained the following components before the degassing treatment:
28 g of PEDOT-PSS dispersion, 26 g of water, 50 g of diethylene
glycol, and 100 mg of 3,5-dimethyl-1-octyne-3-ol. The compositions
had a viscosity of 17.1 mpa.multidot.s after the degassing
treatment and this value was the same as the viscosity of the
compositions, not subjected to the degassing treatment, containing
22% of water. The measurement of the viscosity was performed at
20.degree. C.
[0091] Table 2 shows results obtained by measuring the two species
of compositions A and B for the changing rate of the viscosity. In
the number of days shown in Table 2, the number "0" means that the
measurement was performed just after the preparation and the number
"1" means that the measurement was performed after 24 hours of the
preparation.
2 TABLE 2 Number of Days after Preparation of Composition 0 1 2 5
10 15 20 25 Composition A 0.0 0.2 0.1 0.1 0.3 1.0 1.5 1.0
Composition B 0.0 0.1 0.4 2.7 6.8 14.4 18.3 22.0
[0092] As shown in Table 2, in composition A, the changing rate of
the viscosity remains within a range of .+-.2% when 30 days have
passed after the preparation. In contrast, in composition B, which
is known, the changing rate of the viscosity is 5% or less until
five days have passed after the preparation; however, the changing
rate of the viscosity sharply rises after ten days of the
preparation and reaches 20% after 20 days.
[0093] These results show that the stability of the viscosity of
composition A is extremely high, that is, composition A is
excellent in long-term stability over 30 days after the
preparation. In contrast, in composition B, the changing rate of
the viscosity is outside a range of .+-.5% when 20 days have passed
after the preparation. That is, composition B is inferior in
storage stability to composition A.
[0094] A close examination has not been ever made for such an
influence that is exerted on the surface shape of layers (the
cross-sectional profiles of layers) by the change (changing rate)
of the viscosity of the composition when thin-films are each formed
in corresponding recessions having a minute area by an inkjet
process using compositions having different changing rates of
viscosity. Therefore, the inventors prepared thin-films using
compositions having different changing rates of viscosity, the
changing rates being different from each other when 30 days have
passed after the preparation. The inventors also examined
influences exerted on the surface shape of the obtained thin-films
by the change (changing rate) of the composition viscosity.
[0095] FIGS. 1 and 2 are schematic sectional views showing
situations in which layers 26 (a thickness of about 50 nm) formed
by an inkjet process using three species of compositions having
different changing rates of viscosity are each disposed in
corresponding micro-regions having a recessed shape.
[0096] Base members, shown in FIGS. 1 and 2, including recessions
having a minute area were prepared according to the following
procedure: SiO.sub.2 banks 24 (a thickness of about 100 nm) each
including a SiO.sub.2 layer are each provided on corresponding
substrates 21 having ITO, and predetermined etching treatment was
performed so that the circular recessions having a minute area and
a diameter of 40 .mu.m were arranged. Each recession had a
perpendicular wall (a height of about 100 nm) and a bottom at which
the surface of each substrate 21 including ITO was exposed. Organic
banks 28 (partitions having a thickness of about 2 .mu.m) including
an acrylic material are each provided only on corresponding
SiO.sub.2 banks 24.
[0097] FIG. 1 shows a structure including composition A of the
present invention, that is, a structure including a composition in
which the changing rate of the viscosity is within a range of
.+-.2% when 30 days have passed after the preparation. FIG. 2 shows
a structure including composition B of a comparative example, that
is, a structure including a composition in which the changing rate
of the viscosity is outside a range of .+-.5% after the
preparation.
[0098] FIG. 1 illustrates that a layer 26a including composition A
of an aspect of the present invention has a surface on which the
center region is flat and the periphery region that is in contact
with the wall of each SiO.sub.2 bank 24 is substantially flat as
well as the center region.
[0099] In contrast, a layer 26b including composition B, in which
the changing rate of the viscosity is outside a range of .+-.5%
when 30 days have passed after the preparation, has a surface
having two types of cross-sectional profiles shown in FIG. 2. FIG.
2(a) shows a structure including composition B in which the
changing rate of the viscosity is outside a range of .+-.5% when 10
days have passed after the preparation. In a layer 26b, the center
region of the surface is flat; however, the periphery region of the
layer 26b inclines downward, the periphery region being in contact
with the wall of the SiO.sub.2 bank 24. FIG. 2(b) shows a structure
including composition B in which the changing rate of the viscosity
is outside a range of .+-.20% when 30 days have passed after the
preparation. In a layer 26c, the center region of the surface is
flat; however, the periphery region of the layer 26c inclines
upward, the periphery region being in contact with the wall.
[0100] From the results shown in FIGS. 1 and 2, the inventors have
found that the layer 26a including composition A, in which the
changing rate of the viscosity of composition A is within a range
of .+-.5% when 30 days have passed after the preparation, is
satisfactory in flatness. In particular, the inventors have
confirmed from the above-mentioned experiments that not only the
center of the layer 26a is flat but also the periphery region of
the layer 26a that is in contact with the wall is substantially
flat as well as the center region.
[0101] The solvent, which is a component of composition A that has
a small changing rate of viscosity and is fit for forming layers
having satisfactory flatness, contains a alcohol medium.
[0102] When the content of the glycol medium in the solvent is 40
to 50 percent by weight, the layer flatness can be maintained
within a range of .+-.20%. In particular, the glycol medium is
preferably diethylene glycol or triethylene glycol.
[0103] The organic conductive material, which is a component of the
composition that has a small changing rate of viscosity, can be
dissolved or dispersed in the solvent, and is fit for forming
layers having satisfactory flatness, is preferably a polythiophene
derivatives, a mixture of polydioxythiophene and polystyrene
sulfonic acid, and a mixture of polyaniline and polysulfonic
acid.
[0104] When the solvent contained in the above-mentioned
composition contains an acetylenic alcohol surfactant, the
dispersibility of the organic conductive material, as well as the
solvent, contained in the composition can be enhanced and therefore
the surface tension of the composition can be adjusted. When layers
are formed using the composition by the inkjet process, the
enhancement of the dispersibility prevents inkjet nozzle holes from
being plugged with solid contents in the composition and provides
uniform layers. Furthermore, the adjustment of the surface tension
contributes to maintain the contact angle of the composition,
disposed at the nozzle holes, at an appropriate value and therefore
the composition discharged from the nozzle holes can be reduced or
prevented from flying in an arc, thereby allowing the discharged
composition to fly in a straight line with stability. Furthermore,
when the composition placed on the substrate has an appropriate
surface tension, the wettability of the composition on the
substrate can be controlled, thereby enhancing the layer
flatness.
[0105] The content of the acetylenic alcohol surfactant is
preferably 0.01 to 0.1 percent by weight because the layer flatness
can be maintained within a range of .+-.20% when the thin-films are
each formed in the corresponding minute regions having a recessed
shape.
[0106] When the acetylenic alcohol surfactant has a boiling point
less than or equal to the boiling point of the medium, as well as
the surfactant, contained in the solvent, the surfactant enhances
the efficiency of organic EL elements each including corresponding
layers, including the composition containing the surfactant, each
functioning as a hole injection/transfer layer and also enhances
the life of such elements.
[0107] In particular, the acetylenic alcohol surfactant having the
above advantages includes 3,5-dimethyl-1-octyne-3-ol.
Organic Conductive Layer and Method to Manufacture the Same
[0108] An organic conductive layer according to an aspect of the
present invention includes the above-mentioned composition having
such long-term stability that the changing rate of viscosity is
within a range of .+-.5% when 30 days has passed after the
preparation, as described above. Therefore, flat layers can be
obtained without depending on the storage period of the
composition. Thus, the organic conductive layer having the above
configuration is fit for mass production and contributes to reduce
the manufacturing cost greatly because a step of planarizing the
layer is not necessary after the formation.
[0109] Since the organic conductive layer having the above
configuration is excellent in surface flatness without depending on
the storage period of the composition, another layer placed on the
organic conductive layer can be readily planarized without
depending on the material properties of the placed layer when
electronic devices, such as an organic EL element and an organic
semiconductor device described below are manufactured. Thus, the
organic conductive layer an aspect of the present invention is fit
for the manufacture of such electronic devices including a
plurality of stacked layers.
[0110] A method to manufacture organic conductive layers according
to an aspect of the present invention includes an applying step of
applying the above composition to different portions by an inkjet
process.
[0111] As described above, the composition according to an aspect
of the present invention has such an advantage that the changing
rate of viscosity is small. Therefore, the composition can be
continuously discharged from nozzle holes with stability without
causing such a problem that the nozzle holes are plugged due to a
change in viscosity. Thus, the discharging rate can be maintained
constant during the discharging operation without depending on the
storage period of the composition. In particular, in the organic
conductive layer-manufacturing method including an applying step of
intermittently applying the composition to different portions to
form layers, the discharging rate can be precisely controlled by
the use of the composition, thereby rendering the layer thickness
uniform.
[0112] Furthermore, in an organic conductive or semiconductive
layer- manufacturing method including an applying step of applying
a composition to different portions by an inkjet process, layers
having different characteristics can be formed by feeding the
composition, in which the chemical makeup is gradually varied, to
the nozzle holes or by using inkjet heads each discharging
corresponding materials (compositions) different from each other.
Thus, according to this manufacturing method having the above
configuration, for example, regions having different conductive
characteristics can be readily formed at desired locations on a
substrate.
[0113] The organic conductive layer-manufacturing method includes a
drying step of removing a solvent after the application step.
[0114] Since the method includes the drying step of removing the
solvent, layers that are flat and dense can be obtained with high
reproducibility by removing the solvent from the applied
liquid.
[0115] In particular, the efficiency of removing the solvent from
the obtained layers can be enhanced by performing the drying step
under vacuum conditions. Furthermore, flat organic conductive
layers can be efficiently formed in a shorter time under the
following vacuum conditions: a pressure of 1.333.times.10.sup.-3 Pa
(10.sup.-5 Torr) and a temperature substantially equal to room
temperature.
[0116] The organic conductive layer-manufacturing method includes a
heating step of performing thermal treatment at a temperature of
100.degree. C. or more after the drying step.
[0117] When the organic conductive layers from which the solvent
has been removed in the drying step are subjected to the heating
step of performing thermal treatment at a temperature of
100.degree. C. or more, an organic conductive material contained in
the composition included in the organic conductive layers is
rendered dense, thereby enhancing the adhesion of each organic
conductive layer to a substrate (base layer) or another layer
disposed on the organic conductive layer. The heating step is
advantageous in that the solvent, contained in the composition, for
dispersion or dissolution can be sufficiently removed from the
organic conductive layers.
[0118] When an infrared ray unit is used for a heat source of the
heating step, the organic conductive layers can be heat-treated
without causing the organic conductive layer to be in contact with
the heat source, thereby removing the solvent efficiently.
Organic EL Element and Electronic Device Including the Same
[0119] An organic EL element according to an exemplary embodiment
of an aspect of the present invention and an electronic device,
commonly called an organic EL device, including the organic EL
element will now be described in detail with reference to FIG.
3.
[0120] FIG. 3 is a sectional view showing a principal portion of an
exemplary electronic device including organic EL elements each
including the above-mentioned organic conductive layer according to
an aspect of the present invention, wherein the organic conductive
layer functions as a hole injection/transfer layer. The organic EL
device shown in FIG. 3 includes the organic EL elements having a
configuration in which light is emitted in the direction of a
substrate 1, the organic EL elements being of a substrate-side
light emission type. This technique for using the organic
conductive layer for the hole injection/transport layer is also
applicable to another organic EL element having a configuration in
which light is emitted in the direction of a substrate 12, which is
not shown, this organic EL element being of a sealing-side light
emission type.
[0121] The organic EL device according to an aspect of the present
invention includes the substrate 1; anodes (first electrodes) 3 and
a cathode (second electrode) 9 disposed above a surface of the
substrate 1, each anode 3 and the. cathode 9 forming a pair;
light-emitting layers (EL layers) 7, each disposed between the
corresponding anodes 3 and the cathode 9, including an organic EL
material; hole injection/transport layers 6; and a sealing
substrate 12.
[0122] The anodes 3 are transparent and the cathode 9 is
reflective. The anodes 3 each function as a pixel electrode
connected to each light-emitting pixel functioning as a pixel. The
cathode 9, each light-emitting layer 7, each hole
injection/transport layer 6, and each anode 3 form the organic EL
element according to an aspect of the present invention.
[0123] The hole injection/transport layers 6 and the light-emitting
layers 7 are partitioned with a plurality of partitions (banks) 8
and horizontally arranged in a separated, distributed manner, and
each hole injection/transport layer 6 and light-emitting layer 7
form a pixel. SiO.sub.2 (silicon oxide) 4 is disposed under each
partition 8. The sealing substrate 12 is joined to the substrate 1
with an adhesive layer 11 disposed therebetween. The organic EL
elements, each including the cathode 9, the corresponding
light-emitting layers 7, the corresponding hole injection/transport
layers 6, and the corresponding anodes 3, are sealed with the
sealing substrate 12 and the adhesive layer 11. A surface of the
sealing substrate 12 close to the cathode 9 is covered with a
protective layer 10. TFTs (thin-film transistors) 2 for controlling
currents applied to the anodes 3 are arranged on the substrate 1
and each TFT 2 is a component of a circuit for driving each organic
EL element.
[0124] The organic EL elements included in the electronic device
shown in FIG. 3 each include the organic conductive layer of an
aspect of the present invention which functions as each hole
injection/transport layer 6. The hole injection/transport layer 6
is placed in a region surrounded by the partitions 8 and must have
a flat surface. Since the organic conductive layer according to an
aspect of the present invention is used as the hole
injection/transport layer 6, the center section of the layer
surface is flat and the periphery section of the layer surface as
well as the center section is flat, the periphery section being in
contact with the partitions 8. When each light-emitting layer 7 is
placed on the corresponding hole injection/transport layer 6, the
light-emitting layer 7 has a surface that is flat from the center
section to the periphery section, because the periphery portion of
the organic conductive layer functioning as a base layer is flat.
As a result, light emitted from the light-emitting layer 7 is
propagated in each organic EL element according to predetermined
optical design.
[0125] The organic EL element including the organic conductive
layer functioning as the hole injection/transport layer 6 in which
holes move has high reliability, wherein the organic conductive
layer is satisfactory in surface flatness and has high long-term
reliability. Thus, the organic EL element can provide the
electronic device having high long-term reliability.
[0126] Since the organic EL device is of a substrate-side light
emission type, a material to form the substrate 1 includes a
transparent or high transmissive material in which light can be
transmitted, wherein the transparent or high transmissive material
includes, for example, transparent glass; quartz crystal; sapphire;
and a transparent synthetic resin such as polyester, polyacrylate,
polycarbonate, or polyether ketone. In this case, the sealing
substrate 12 may include a metal laminate film.
[0127] In contrast, when the organic EL device is of a sealing-side
light emission type, the following material may be used: ceramic,
such as alumina; a metal sheet, such as a stainless sheet,
subjected to insulating treatment, such as surface oxidation; a
thermosetting resin; or a plastic resin. If a layer including a
high reflective material is placed on the back of each anode, a
substrate including the same material as that of the organic EL
device that is of a substrate-side light emission type may be used.
The sealing substrate 12 includes such a transparent or high
transmissive material in which light can be transmitted.
[0128] The anodes 3 preferably include a high transmissive material
containing indium tin oxide (ITO) and having a large work function.
Each hole injection/transport layer 6 is preferably the organic
conductive layer including the composition according to the present
invention, that is, the composition in which the changing rate of
the viscosity is within a range of .+-.5% when 30 days have passed
after the preparation, as described above.
[0129] A material to form the light-emitting layers 7 includes
polymers containing an organic luminescent dye that is of a
fluorescent high or low molecular type or a low molecular weight
dye dispersed therein. That is, various luminescent materials, such
as fluorescent materials and phosphorescent materials can be used.
Among conjugated polymers to form the luminescent materials, a
polymer having an arylene vinylene structure or a polyfluorene
structure is particularly preferable. Low molecular weight
fluorescent materials include naphthalene derivatives; anthracene
derivatives; perylene derivatives; dyes, such as polymethine dyes,
xanthene dyes, coumarin dyes, and cyanine dyes; metal complexes
containing 8-hydroquinone or a derivative thereof; aromatic amines;
tetraphenylcyclopentadiene derivatives; and known materials
disclosed in Japanese Unexamined Patent Application Publication No.
57-51781 or Japanese Unexamined Patent Application Publication No.
59-194393. The cathode 9 is preferably a metal electrode containing
lithium (Li), calcium (Ca), magnesium (Mg), fluoride thereof,
aluminum (Al), gold (Au), silver (Ag), or the like.
[0130] An electronic transfer layer or an electronic injection
layer may be placed between the cathode 9 and each light-emitting
layer 7 according to needs.
[0131] The organic EL device of this exemplary embodiment is of an
active matrix type and therefore a plurality of data lines and
scanning lines, which are not shown, are arranged above the
substrate 1 in a grid in actual. In the organic EL element, pixels
that are partitioned with the data lines and scanning lines and
arranged in a matrix are connected to driving TFTs, such as
switching transistors and driving transistors. Therefore, when
driving signals are supplied through each data line and scanning
line, a current is applied between electrodes of each pixel,
thereby causing each light-emitting layer 7 of the organic EL
element to emit light. That is, the pixel is turned on.
Method to Manufacture Organic EL Elements and Method to Manufacture
Electronic Device Including the Same
[0132] A method to manufacture an organic EL device according to an
exemplary embodiment of the present invention will now be described
with reference to FIG. 3. FIG. 3 is a sectional view showing a
principal portion of the organic EL device according to the
exemplary embodiment of the present invention.
[0133] Anodes 3 are provided above a substrate 1, on which TFTs 2
each functioning as a driving circuit of an organic EL element are
arranged, using indium tin oxide (ITO). SiO.sub.2 banks 4 are then
provided above the resulting substrate 1.
[0134] Partitions 8 including a resin are then each provided on the
corresponding SiO.sub.2 banks 4. Hole injection/transport layers 6
having a thickness smaller than that of the SiO.sub.2 banks 4 are
each provided in corresponding regions that are surrounded by the
SiO.sub.2 banks 4 and disposed on the anodes 3. Light-emitting
layers 7 are each provided in regions that are surrounded by the
partitions 8 and disposed on the SiO.sub.2 banks 4 and the hole
injection/transport layers 6.
[0135] A cathode 9 is then provided over the light-emitting layers
7 and the partitions 8 including organic banks.
[0136] According to the above procedure, the following components
that form each organic EL element are obtained: the cathode 9, each
light-emitting layer 7, each hole injection/transport layer 6, and
each anode 3.
[0137] A protective layer 10 is then provided on the upper surface
of the cathode 9, which is a component of the organic EL element.
An adhesive agent is applied onto the protective layer 10 and the
organic EL elements and a sealing substrate 12 is pressed on the
adhesive agent, thereby forming an adhesive layer 11 and fixing the
sealing substrate 12.
[0138] According to the above procedure, an electronic device
(organic EL device) including the organic EL elements according to
an aspect of the present invention and driving circuits therefore
is obtained.
[0139] In the above-mentioned manufacturing steps, the above layers
may be prepared by any thin-film preparing method; however, at
least the hole injection/transport layers 6 and the light-emitting
layers 7 are preferably prepared by an inkjet process.
[0140] FIG. 4 is a schematic sectional view showing a configuration
of the substrate having no hole injection/transport layers 6 to be
formed by an inkjet process. In FIG. 4, reference numeral 1
represents the substrate, reference numeral 3 represents the
anodes, reference numeral 4 represents the SiO.sub.2 banks, and
reference numeral 8 represents the partition banks including an
organic material. Regions surrounded by the anodes and banks
correspond to pixel regions.
[0141] FIGS. 5 to 8 are schematic sectional views showing a step of
manufacturing the organic EL device according to an exemplary
embodiment of the present invention. A procedure to prepare the
hole injection/transport layers 6 and the light-emitting layers 7
by an inkjet process is herein described in detail.
[0142] FIG. 5 is a schematic sectional view showing a configuration
of the substrate having no hole injection/transport layers 6. The
following situation is illustrated: a composition 6a to form the
hole injection/transport layers 6 is discharged from nozzle holes
15 of an inkjet head 14 toward the surfaces of the anodes 3
surrounded by the SiO.sub.2 banks 4 and the organic partition banks
8. In a step before the discharging step, the anodes 3 and the
SiO.sub.2 banks have been surface-treated so as to have an affinity
to ink and the organic partition banks 8 have been surface-treated
so as to have an ink-repellent property. In the surface-treatment
step, O2 plasma treatment and CF4 plasma treatment were
continuously performed under atmospheric temperature.
[0143] FIG. 6 is a schematic sectional view illustrating a
situation after each hole injection/transport layer 6 is formed by
providing the composition 6a in a pixel and then drying the same.
Since the composition 6a contains an organic conductive material
and at least one species of solvent and the changing rate of the
composition viscosity is within a range of .+-.5% when 30 days have
passed after the preparation, the periphery portion of the surface
of the hole injection/transport layer 6, as well as the center
portion, remains flat without depending on the elapsed time after
the preparation, wherein the periphery portion is in contact with
each SiO.sub.2 bank 4.
[0144] FIG. 7 is a schematic sectional view illustrating such a
situation that a composition 7a to form the light-emitting layers 7
each placed on the corresponding hole injection/transport layers 6
is disposed in each pixel.
[0145] FIG. 8 is a schematic sectional view illustrating such a
situation that a sealing layer 13 is disposed on the cathode 9
formed according to the following procedure. The light-emitting
layer-forming composition 7a provided on each hole
injection/transport layer 6 is dried so that each light-emitting
layer 7 is formed. The cathode 9 is then formed over the
light-emitting layer 7 and each organic bank (partition) 8. The
term sealing layer 13 is a generic name for the protective layer
10, the adhesive layer 11, and the sealing substrate 12 shown in
FIG. 3.
[0146] As shown in FIG. 6, when the hole injection/transport layers
6 are formed by an inkjet process using the hole
injection/transport composition having satisfactory storage
stability, thin-films satisfactory in flatness can be each
precisely formed in corresponding minute regions surrounded by the
banks 4 and 8. The organic EL elements including the hole
injection/transport layers 6 formed by an inkjet process have such
an advantage that the element life is extremely long.
[0147] Elements having the following configuration were prepared: a
configuration in which each hole injection/transport layer 6 formed
using one of two species of compositions A and B is placed between
a cathode and an anode without forming the light-emitting layer.
The elements were sequentially examined for changes in resistance
after the preparation of ink. Table 3 shows the measurement result
of the resistance of each element formed using one of the
compositions on the day when the ink has been prepared or when 10,
20, or 30 days have passed after the preparation of the ink.
[0148] The above element has a configuration in which an anode
including ITO, the hole injection/transport layer including
composition A or B, a cathode including Al arranged in that order.
This configuration includes the same substrate as that shown in
FIG. 4.
[0149] In order to form the hole injection/transport layer 6 using
composition A or B, an inkjet process was employed.
[0150] In Table 3, the term elements A refers to elements each
including the hole injection/transport layer 6 formed using
composition A and the term elements B refers to elements each
including the hole injection/transport layer 6 formed using
composition B. In the number of days shown in Table 3, the number
"0" refers to that elements are each formed using the corresponding
compositions on the day when the ink has been prepared and examined
for the resistance.
3 TABLE 3 Number of Days after Preparation of Ink 0 10 20 30
Elements A 1.5 .times. 10.sup.-5 1.6 .times. 10.sup.-5 1.9 .times.
10.sup.-5 1.5 .times. 10.sup.-5 Elements B 1.5 .times. 10.sup.-5
3.0 .times. 10.sup.-5 1.2 .times. 10.sup.-6 4.5 .times.
10.sup.-7
[0151] As shown in Table 3, in elements A each including the hole
injection/transport layer 6 including composition A according to an
aspect of the present invention, the resistance of an element
formed using the composition when 20 days have passed after the
preparation of the composition is substantially the same as that of
an element formed using the composition just after the preparation
(0 day). This tendency is maintained until 30 days have passed
after the preparation of the element.
[0152] In contrast, in elements B including the hole
injection/transport layer 6 including related art composition B,
the resistance of an element formed using the composition when 10
days have passed after the preparation of the composition is two
times larger than that of an element formed using the composition
just after the preparation (0 day). The resistance of an element
formed using the composition when 20 days have passed after the
preparation of the composition increases in value by 10 times and
the resistance of an element formed using the composition when 30
days have passed increases in value by more than 100 times.
[0153] The above result shows that elements A each including the
hole injection/transport layer 6 including composition A according
to the present invention have more satisfactory long-term stability
in resistance as compared with elements B including conventional
composition B. That is, elements A each including the hole
injection/transport layer 6 including composition A according to
the present invention have smaller changes in conductive property
as compared with elements B irrespective of the storage period of
the compositions.
[0154] The inventors prepared organic EL element A' including blue
light-emitting layers 7 each disposed on the corresponding hole
injection/transport layers 6 including composition A according to
the present invention and also prepared organic EL element B'
including the blue light-emitting layers 7 each disposed on the
corresponding hole injection/transport layers 6 including related
art composition B. The inventors then examined two organic EL
elements A' and B' for the element life. The term element life
herein refers to the time that elapses until the luminance of an
element decreases by half when a constant current is continuously
applied to the element. As a result, it was confirmed that element
A' has an element life 2.5 times longer than that of element B'.
The long life of element A' is presumed to be due to the effect of
the composition having long-term stability.
[0155] Since the solvent, which is a component of the composition
according to an aspect of the present invention, contains the
glycol medium, the composition has an extremely small changing rate
of viscosity, that is, the composition is stable. The result of the
following examination will now be described: the examination of the
optimum content of the glycol medium in the solvent.
[0156] Diethylene glycol (a boiling point of245.degree. C.), which
is one of glycol media, was employed, and compositions A each
containing corresponding solvents were prepared in advance, the
content of diethylene glycol in the solvents being 0, 15, 30, 40,
45, 50, 55, and 60 percent by weight. A plurality of elements A,
each including the corresponding hole injection/transport layers 6,
each including corresponding compositions A having the different
contents were prepared. Element A containing the solvent having a
diethylene glycol content of, for example, 45 percent by weight is
herein referred to as element A(45). When the number inside the
parentheses is 0, the solvent does not contain diethylene
glycol.
[0157] Table 4 shows results obtained by measuring elements A,
having different diethylene glycol contents (the unit is percent by
weight), for the discharging properties of the compositions, the
pixel flatness, and the layer profile.
[0158] The term pixel flatness refers to the ratio (the unit is
.+-.%) of the thickness of each hole injection/transport layer 6 to
the distance between the highest location (most thick portion) and
the lowest location (most thin portion) of on the surface of the
hole injection/transport layer 6. Symbol x represents a sample that
cannot be evaluated for the pixel flatness. The term layer profile
refers to a surface shape of a sectional view of a layer and is
expressed by the term convex shape, flat shape, or concave. The
actual layer thickness (profile of a sectional view) was measured
using a probe profilometer. The discharging property is an
indicator showing whether plugging is caused or not and whether the
discharged composition flies in a straight line or not when
composition A is discharged from nozzle holes by an inkjet process.
Symbol A represents that both the items are satisfactory, Symbol B
represents that one of the items is satisfactory, and Symbol C
represents that both the items are not satisfactory.
4TABLE 4 Diethylene glycol content 0 15 30 40 45 50 55 60 Pixel
flatness x >50 40 20 18 15 15 25 Layer profile Convex Convex
Convex Slightly Slightly Flat Flat Concave Convex Convex
Discharging A A A A A A A A
[0159] Table 4 shows that the pixel flatness can be controlled
within a range of .+-.20, the layer profile can be maintained
substantially flat, and the discharging property is satisfactory
when the diethylene glycol medium content in the solvent is
controlled within a range of 40 to 50 percent by weight.
[0160] Since the solvent, which is a component of the composition
according to an aspect of the present invention, contains an
acetylenic alcohol surfactant in addition to the alcohol medium,
the dispersibility is satisfactory and the surface tension is low.
The result of the following examination will now be described: the
examination of the optimum content (percent by weight) of the
acetylenic alcohol surfactant.
[0161] Table 5 shows the element efficiency, element life, and
pixel flatness obtained by examining blue light-emitting elements
A' prepared using 3,5-dimethyl-1-octyne-3-ol (SF 61, manufactured
by Air Products and Chemicals Inc. and herein referred to as SF 61,
having a boiling point of 160.degree. C.), which is an example of
the acetylenic alcohol surfactant.
[0162] Diethylene glycol, which is one of glycol media, was used
and the content was set to 50 percent by weight.
[0163] The term element efficiency refers to a luminance per unit
current (candela/ampere) and is herein expressed by an index value
obtained by normalizing the luminance of an element containing no
SF 61 to an index value of 1. The term element life refers to the
time that elapses until the luminance of a light-emitting element
decreases by half when a constant current is continuously applied
to the element and is herein expressed by an index value obtained
by normalizing the time of the element containing no SF 61 to an
index value of 1. The term pixel flatness refers to the ratio (the
unit is .+-.%) of the thickness of each hole injection/transport
layer 6 to the distance between the highest location (most thick
portion) and the lowest location (most thin portion) of on the
surface of the hole injection/transport layer 6. Symbol x
represents a sample that cannot be evaluated for the pixel
flatness.
5TABLE 5 SF 61 Content 0 0.01 0.05 0.1 0.5 Element efficiency 1.0
1.0 1.2 1.05 1.2 Element Life 1.0 1.0 1.0 1.1 0.8 Pixel Flatness
>50 20 15 15 25
[0164] Table 5 shows that the pixel flatness can be controlled
within a range of .+-.0 and the element properties, such as the
element efficiency and the element life are satisfactory when the
SF 61 content is controlled within a range of 0.01 to 0.1.
[0165] Table 6 shows the element efficiency, element life, and
pixel flatness obtained by examining blue light-emitting elements
A' prepared using 3,5-dimethyl-4-octyne-3,6-dithiol (SF 82W,
manufactured by Air Products and Chemicals Inc. and herein referred
to as SF 82W, having a boiling point of 220.degree. C.), which is
an example of the acetylenic alcohol surfactant. Other preparing
conditions are the same as those shown in Table 5.
6TABLE 6 SF 82W Content 0 0.01 0.05 0.1 0.5 Element efficiency 1.0
1.1 1.0 0.9 0.7 Element Life 1.0 0.9 0.95 0.9 0.7 Pixel Flatness
>50 20 15 10 10
[0166] Table 6 shows that the pixel flatness can be controlled
within a range of .+-.20 and the element efficiency and the element
life are satisfactory when the SF 82W content is controlled within
a range of 0.01 to 0.1. For SF 82, an increase in content enhances
the flatness but deteriorates the element properties.
[0167] According to the results of the above-mentioned two tables 5
and 6, since the solvent, which is a component of the composition
according to an aspect of the present invention, contains an
acetylenic alcohol surfactant in addition to the glycol medium, the
dispersibility is satisfactory. Furthermore, the element efficiency
and the element life are substantially the same as those of an
element containing no surfactant and the flatness of obtained pixel
extremely satisfactory when the content (percent by weight) of the
acetylenic alcohol surfactant is controlled within a range of 0.01
to 0.1.
[0168] Organic EL element C containing the following surfactant
instead of SF 61 (a boiling point of 160.degree. C.) and SF 82W (a
boiling point of 220.degree. C.) is decreased in element efficiency
by 20% and decreased in element life by 30% as compared with the
above element A': surfactant S104 (manufactured by Air Products and
Chemicals Inc.) having a boiling point higher than that of
diethylene glycol (a boiling point of 245.degree. C.).
[0169] The inventors have concluded based on this result that the
above-mentioned acetylenic alcohol surfactant preferably has a
boiling point that is less than or equal to that of the medium,
which is a component of the solvent as well as this surfactant.
Organic Semiconductor Element
[0170] FIG. 9 is a schematic sectional view showing an example of
an organic semiconductor element according to an aspect of the
present invention.
[0171] The organic semiconductor element having a configuration
shown in FIG. 9 includes a substrate 901 and a gate electrode 902
disposed thereon. A gate insulating layer 903 including an
insulating material having a large dielectric constant is disposed
over the substrate 901 and the gate electrode 902, and a channel
904 is disposed on the gate insulating layer 903. A source
electrode 905 and a drain electrode 906 are arranged on the channel
904. These components form the organic semiconductor element for
preparing a thin-film transistor. In this example, the three
electrodes, that is, the gate electrode 902, the source electrode
905, and the drain electrode 906 were prepared using the
composition according to an aspect of the present invention by an
inkjet process.
[0172] As described above, since the electrodes according to an
aspect of the present invention are flat, electrons and holes
moving in the electrodes containing the organic semiconductive
layer can extremely constantly move therein. That is, constant
current flows can be maintained in the above electrodes for a long
period and therefore organic semiconductor elements having high
long-term reliability can be provided.
[0173] In FIG. 9, the gate electrode 902, the source electrode 905,
and the drain electrode 906 among conductive portions included in
an integrated circuit include the organic conductive layer
containing the composition according to an aspect of the present
invention; however, the channel 904 may include the organic
conductive layer according to an aspect of the present invention.
Furthermore, the organic conductive layer may be used to form
wiring lines, not shown, to connect such thin-film transistors.
[0174] A method to manufacture organic semiconductor elements,
wherein a source, a drain, a gate and/or wiring lines, which are
conductive portions included in an integrated circuit, including
the above-mentioned organic conductive layer are formed by an
inkjet process.
[0175] In the organic semiconductor element-manufacturing method,
having the above constitution, according to an aspect of the
present invention, functional layers can be formed in a pattern by
an inkjet process, which is a simple process. Therefore, a
large-scale vacuum process and photolithographic process, which
must be used to manufacture layers by a related art manufacturing
method, need not to be used to form such organic semiconductor
elements having high long-term reliability.
[0176] Thus, the organic semiconductor element-manufacturing method
according to an aspect of the present invention greatly contributes
to the production of inexpensive organic semiconductor elements
because the manufacturing cost can be greatly saved.
Electronic Apparatus
[0177] An exemplary electronic apparatus including an electronic
device including the above-mentioned organic EL device will now be
described.
[0178] FIG. 10 is a perspective view showing an example of a mobile
phone. In FIG. 10, reference numeral 1000 represents a mobile phone
body and reference numeral 1001 represents a display section
including the above organic EL device (electronic device).
[0179] FIG. 11 is a perspective view showing an example of a
watch-type electronic apparatus. In FIG. 11, reference numeral 1100
represents a watch body and reference numeral 1101 represents a
display section including the above organic EL device (electronic
device).
[0180] FIG. 12 is a perspective view showing an example of a
portable information processor, such as a word processor or a
personal computer. In FIG. 12, reference numeral 1200 represents
the information processor, reference numeral 1202 represents an
input section, such as a key board, reference numeral 1204
represents an information processor body, and reference numeral
1206 represents a display section including the above organic EL
device (electronic device).
[0181] Since the electronic apparatuses shown in FIGS. 10 to 12
each include the organic EL device (electronic device) of the above
exemplary embodiment, the luminance of the display sections can be
maintained constant over the long term. Thus, electronic
apparatuses having high long-term reliability can be provided. When
these electronic apparatuses each include the above-mentioned
organic semiconductor element, the manufacturing cost of the
electronic apparatuses can be saved.
[0182] The technical scope of the present invention is not limited
to the above exemplary embodiments and various modifications may be
performed within the scope of the present invention. Particular
materials and layer configurations described in the exemplary
embodiments each show only an example and various modifications may
be performed.
[0183] In the organic EL device of the above exemplary embodiment,
for example, the anodes 3 function as pixel electrodes and the
cathode 9 functions as a counter electrode. However, the cathode 9
may be used as a pixel electrode and the anodes 3 may be used as
counter electrodes.
Advantages
[0184] As described above, a composition according to an aspect of
the present invention contains an organic conductive material and
at least one species of solvent. Since the changing rate of the
viscosity is within a range of .+-.5% when 30 days have passed
after the preparation, organic conductive layers having
satisfactory surface flatness and stability can be formed using
this composition without depending on the time that has elapsed
after the preparation of the composition.
[0185] The above composition is satisfactory in long-term storage
property because the changing rate of the viscosity is small.
Therefore, since the composition can be manufactured at low cost by
a mass production process, the composition can be marketed alone
and used in various industrial applications.
[0186] Since flat organic conductive layers can be formed by an
inkjet process, in which an expensive vacuum unit is not necessary,
using the above composition with high reproducibility, such organic
conductive layers can be provided by an organic conductive
layer-manufacturing method according to an aspect of the present
invention at low cost.
[0187] In particular, in the organic conductive layer-manufacturing
method according to an aspect of the present invention, the
composition, in which the viscosity is hardly changed with the
passage of time, is used. The method includes an applying step of
applying the composition to different portions. Thus, layers having
a surface in which the periphery portion in contact with a wall is
flat as well as the center portion can be readily obtained when
such layers are each formed in corresponding minute regions.
[0188] An organic EL device (electronic device) in which the time
that elapses until the luminance decreases by half is long can be
obtained by preparing hole injection/transport layers, included in
organic EL elements, using the organic conductive layers.
[0189] When a source, a drain, a gate and/or wiring lines among
conductive portions included in an integrated circuit include the
above-mentioned organic conductive layer, electrons and holes
moving in these conductive portions can smoothly flow. Thus,
organic semiconductor elements having high long-term reliability
can be obtained.
[0190] Furthermore, an electronic apparatus including the
above-mentioned organic EL device and/or organic semiconductor
elements has performance that can be maintained over the long term.
An electronic apparatus including this electronic apparatus has
greatly enhanced long-term reliability.
* * * * *